1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device having a pattern for position registration for cutting a fuse element formed on a semiconductor chip surface by irradiating a laser beam with high accuracy.
2. Description of the Related Art
A laser trimming method for adjusting analog characteristics is known in a device of an analog semiconductor integrated circuit. For example, the laser trimming method is described in Japanese Laid-Open (Kokai) Patent No. 5-13670. In this method, after integrated circuits are two-dimensionally patterned in a semiconductor wafer, electric characteristics of each integrated circuit are measured in a wafer state. Next, a fuse element arranged in one portion of wiring is selected to adjust the analog characteristics and is cut by irradiating a laser beam. The analog characteristics of the integrated circuit can be conformed to desirable characteristics by selectively cutting the fuse element by such a laser trimming method. A pattern for position registration is arranged on a semiconductor wafer surface to irradiate the laser beam to a predetermined fuse element. FIG. 3A is a plan view of a conventional laser trimming position registration pattern. FIG. 3B is a cross-sectional view of the conventional laser trimming position registration pattern. FIG. 3C is a view showing a change in light reflecting amount when this pattern for laser trimming position registration is scanned along the direction of a line C-Cxe2x80x2 by the irradiation of the light beam. As shown in FIG. 3A, the conventional laser trimming position registration pattern is constructed by a so-called theta mark 301, an X-direction trimming mark 302 and a Y-direction trimming mark 303. The theta mark 301 is arranged on a scribe line 203 to perform a relative rough position registration operation with respect to a rotating direction of the semiconductor wafer. The X-direction trimming mark 302 and the Y-direction trimming mark 303 are arranged to perform an accurate position registration operation with respect to each of semiconductor integrated circuits 201 repeatedly arranged. The theta mark 301 is desirably formed in a characteristic shape different from that of a pad area 202, etc. within the semiconductor integrated circuits 201 so as to automatically recognize an image.
In an example of FIG. 3A, the shape of the theta mark 301 is of a key type, but may be set to another shape if this shape is a singular shape and is easily recognized.
As shown in FIG. 3B, in the conventional position registration pattern, a square aluminum film 105 is arranged on a first insulating film 102 constructed by a silicon oxide film arranged on a silicon substrate 101. When the light beam is scanned along the direction of the line C-Cxe2x80x2 of FIG. 3A, a light reflecting pattern is obtained as shown in FIG. 3C since reflectivity of the aluminum film 105 is high. A position relation between the position registration pattern and the fuse element constructed by a polycrystal silicon film of the integrated circuit is determined at a designing time. Accordingly, the coordinates of a desirable fuse element are calculated by detecting the position registration pattern by the irradiation of the light beam, and the fuse element can be selectively trimmed by irradiating the laser beam to this coordinate place.
However, in the conventional laser trimming, no accurate position registration operation can be performed since the fuse element and the position registration pattern are formed by different thin films. Namely, when the pattern for position registration is detected by a pattern of aluminum and the polycrystal silicon film as the fuse element is laser-trimmed, the position of a laser irradiating area 32 is shifted from the fuse element 31 as shown in FIG. 4. Since an energy distribution of the laser irradiating area 32 is set to a Gaussian distribution, energy intensity in a laser irradiating end portion is low. Accordingly, when there is a large shift in alignment between patterning of the polycrystal silicon film and patterning of the aluminum film in a wafer process, a problem exists in that no fuse element can be stably cut. Reference numerals 33 and 34 respectively designate a burning portion of a foundation and a portion left in the fuse cut.
Therefore, an object of the present invention is to provide a method of manufacturing a semiconductor device capable of precisely performing position registration and trimming operations with respect to a fuse element of a semiconductor chip without increasing the number of normal semiconductor integrated circuit manufacturing processes. Another object of the present invention is to make a fuse element area compact and reduce cost by improving a position registration accuracy of trimming.
To solve the above-mentioned problems, the present invention uses the following means.
(1) A semiconductor device is constructed by semiconductor integrated circuits repeatedly arranged two-dimensionally in a matrix shape on the surface of a semiconductor wafer through scribe lines, a fuse element for laser trimming arranged in the semiconductor integrated circuits, and a pattern for laser trimming position registration arranged on the surface of the semiconductor wafer. The pattern for laser trimming position registration is constructed by a high light reflectivity area and a low light reflectivity area. The high light reflectivity area is formed by a high light reflectivity film formed on a flat foundation. The low light reflectivity area is formed by a high light reflectivity film constructed by the same thin film as the fuse element for laser trimming and formed on the pattern of a grid, stripe or dot shape for causing irregular reflection of light.
(2) In the semiconductor device described in the item (1), the pattern for laser trimming position registration is constructed by the high light reflectivity area and the low light reflectivity area surrounded by the high light reflectivity area.
(3) In the semiconductor device describe in the item (1), the pattern for laser trimming position registration is constructed by the low light reflectivity area and the high light reflectivity area surrounded by the low light reflectivity area.
(4) In the semiconductor device described in the item (1), the fuse element for laser trimming is constructed by a polycrystal silicon thin film.
(5) In the semiconductor device described in the item (1), the high light reflectivity film is constructed by aluminum.
The present invention provides a manufacturing method capable of manufacturing the semiconductor device described in the above items (1) to (5) without increasing the number of normal manufacturing processes of the semiconductor integrated circuits.